Persons engaging in skin diving shall mark the water areas where such operations are being conducted with buoyed flags of sufficient size so that they may be seen at a distance of not less than one hundred yards under normal visibility conditions; provided, that where skin diving operations are conducted between the hours of sunset and sunrise, artificially illuminated marker buoys shall be provided which are visible at a distance of not less than one hundred yards under normal visibility conditions. Skin diving shall not be conducted so as to unreasonably interfere with normal operations of vessels. (Ord. 427 (part), 1976).